Might want to give Disney a call to be sure, but I think you'll be ok in most of the resort restaurants.
If you want to chance it you can always stop but the reservation desks and see if there are any cancellations. We tried this same thing at Tusker House on our anniversary trip. They turned us away and there were only two of us. We were told they don't accept walk-ups. I can't for the life me believe that there wasn't a two seat table somewhere in there.
I know there are folks who aren't big on planning your dining but my suggestion is if there's somewhere you want to eat, air on the side of caution and make a reservation.
Just remember that on October 31st, Disney will require a Credit Card hold on all table service and show ADRs. Requiring a 24 hour notice of cancellation or $10 per person will be charged to the credit card.
Some people are like Slinkies.
They aren't really good for anything,
but they still bring a smile to my face when I push them down a flight of stairs.
Friends are Gods way of apologizing to us for our families.